Image forming apparatus for forming image on record medium

ABSTRACT

A record medium determining device  1 , which determines a kind of a record medium  16  by irradiating a laser light  17  to a surface of the record medium  16 , detecting a received light position and a received light intensity of a reflected light  18  by a line sensor  14 , and comparing a distribution state of the received light position and the received light intensity with a previously determined distribution state, is disposed on the upstream side of a record medium conveyance path  653  with respect to a fixing unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus for formingan image on a record medium, which includes a record medium determiningdevice to irradiate a laser light to the record medium, to detect areflected light thereof, and to determine the kind of the record mediumfrom the distribution state of the reflected light.

2. Description of the Related Art

In order to perform excellent image formation in an image formingapparatus such as a copier or a printer, it is necessary to adjust aprinting method according to the kind of a record medium, such as asheet, on which an image is formed. For example, unless the printingmethod is adjusted in a case where printing is performed on a plainpaper and a case where printing is performed on an OHP sheet, anexcellent image can not be obtained.

In an early model, although an operator manually selects the kind of arecord medium, since there is a case where an erroneous selection ismade, the development of a device to detect the kind of the recordmedium has been advanced.

In the related art, there is proposed a device in which a light isirradiated to a record medium, and a reflected light thereof and atransmitted light thereof are detected (for example, JP-A-2006-58261).

This is such that with respect to the light from a first light emittingsource, the received light amount of the transmitted light is detectedby a first light receiving element disposed at a position opposite tothe first light emitting source across the record medium, and withrespect to the light from a second light emitting source, the receivedlight amount of the reflected light is detected by a light receivingelement disposed on the same side as the second light emitting sourcewith respect to the record medium, and these received light amounts arecompared with threshold values to determine the kind of the recordmedium.

However, in this technique, there is a problem that although it ispossible to determine record media, like an OHP sheet and a plain paper,in which the received light amounts of the transmitted lights and thereceived light amounts of the reflected lights are much different fromeach other, when the received light amounts of the transmitted lightsand the received light amounts of the reflected lights becomeapproximate to each other like a plain paper and a recycle plain paper,the accuracy of determination is reduced.

In order to solve this problem, there is proposed a device in which alight is irradiated to a record medium, and a reflected light thereof isdetected by an area sensor (for example, JP-A-2003-205654).

This is such that the reflected light is received by a two-dimensionalsurface, an average value, a maximum value and a minimum value arecalculated from the amount of received light, and they are compared withthreshold values to determine the kind of the record medium.

However, as described later, in this technique, the range of thereflected light which can be received by the area sensor is limited, andthere is a problem that the kind of the record medium which can bedetermined from the pattern of the detectable reflected light islimited.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an image formingapparatus for forming an image on a record medium, which includes arecord medium determining device to determine a kind of the recordmedium by irradiating a laser light to a surface of the record medium,detecting a received light position and a received light intensity of areflected light thereof, and comparing a distribution state of thereceived light position and the received light intensity with apreviously determined distribution state.

In an aspect of the present invention, an image forming apparatus forforming an image on a record medium includes a record medium determiningdevice including

a laser light source to irradiate a laser light to a surface of therecord medium,

a line sensor to receive a reflected light of the laser light from therecord medium and to output an output signal converted into an electricsignal, wherein the line sensor detects a received light position in theline sensor having received the reflected light and a received lightintensity of the received reflected light from the output signal, and

a signal processing device to determine a kind of the record medium bycomparing a distribution state of the received light position and thereceived light intensity with a previously determined distributionstate.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view showing the outline of a record mediumdetermining device.

FIG. 2 is a view showing a structural example of a signal processingdevice.

FIG. 3 is a view showing the outer appearance of a line sensor.

FIG. 4 is a view showing a positional relation among a laser lightsource, a line sensor, and a record medium.

FIG. 5 is a view showing detection results of a case where a recordmedium is a recycled paper.

FIG. 6 is a view showing detection results of a case where a recordmedium is a plain paper.

FIG. 7 is a view showing detection results of a case where a recordmedium is a glossy paper.

FIG. 8 is a view in which ranges where reflected light can be detectedare compared.

FIG. 9 is a view showing a structural example of an image formingapparatus.

FIG. 10 is a view showing the vicinity of a record medium conveyancepath in detail.

DETAILED DESCRIPTION OF THE INVENTION

Throughout this description, the embodiments and examples shown shouldbe considered as exemplars, rather than limitations on the apparatus andmethods of the present invention.

Hereinafter, an embodiment of a particle detecting apparatus of theinvention will be described in detail by use of the drawings.

<Record Medium Determining Device>

First, a record medium determining device will be described.

FIG. 1 is a structural view showing the outline of the record mediumdetermining device of an embodiment. The record medium determiningdevice 1 of the embodiment includes a laser light source 13 to irradiatea laser light 17 to a surface of a record medium 16, a laser lightsource drive device 11 to supply power to the laser light source 13 andto control irradiation of the laser light 17, a line sensor 14 toreceive a reflected light 18 of the laser light 17 reflected by therecord medium 16 and to output an output signal converted into anelectric signal, and a signal processing device 12 to receive the outputsignal, to perform a specified determination processing and to determinethe kind of the record medium 16.

The laser light source 13 is a device to irradiate the laser light 17,and the kind of the laser light and the principle of the laser lightoscillation are not restricted. Although the wavelength of the laserlight 17 may be any wavelength as long as the after-mentioned linesensor 14 can detect, a visible light is desirable in view of handling.The intensity of the laser light 17 can be arbitrarily set within arange where it is reflected by the record medium 17 and reaches the linesensor 14 at such intensity that it can be detected by the line sensor14.

FIG. 2 is a view showing a structural example of the signal processingdevice 12. The signal processing device 12 includes an A/D converter 12Awhich receives the output signal from the line sensor 14 and convertsanalog data into digital data, and a determination device 12B to performa specified processing on the output signal converted into the digitaldata and to output the kind of the record medium 16.

The determination device 12B can be constructed, for example, asdescribed below. The determination device 12B includes a processor suchas a digital signal processor, a memory to store data and a program, anda communication device to output data to an external device. Thisprocessor reads the program describing a processing procedure todetermine the record medium 16 from the memory and executes it, so thatthe inputted output signal is processed, and the determination result isoutputted.

FIG. 3 is a view showing the outer appearance of the line sensor 14. Theline sensor 14 includes, for example, a linear sensor 14A to receive alight and to convert it into an electric signal, and a conversion deviceto amplify and convert the electric signal converted by the sensor 14Ato a state suitable for output.

As the sensor 14A, what is obtained by arranging plural optical sensorslinearly may be used, or one vertically long optical sensor may be used.In the case where the plural optical sensors are used, the light sensorsmay be arranged in one line, may be arranged to be alternately shifted,or may be arranged in two or more lines.

In the case where the record medium determining device 1 of theembodiment is installed in an image forming apparatus to exclusivelyprint the record medium 16 of a small size, it is necessary to use thesmaller line sensor 14, and in the case where it is installed in animage forming apparatus, such as a copier, to print also the recordmedium of a large size, it is necessary to use the larger line sensor14. As stated above, the width W of the sensor 14A in the longitudinaldirection can be suitably selected according to the size of the recordmedium 16 to be determined.

From the background as stated above, it is desirable that the length ofthe sensor 14A of the line sensor 14 in the longitudinal direction isnot less than 5 mm and not larger than the length of the maximum recordmedium to be determined in the longitudinal direction.

FIG. 4 is a view showing a positional relation among the laser lightsource 13, the line sensor 14 and the record medium 16. The laser lightsource 13 and the line sensor 14 are disposed at the same side withrespect to the record medium 16. The line sensor 14 is disposed at aposition where the reflected light 18 of the laser light 17 irradiatedfrom the laser light source 13 and reflected by the record medium 16 isincident on the sensor 14A.

It is desirable that the laser light source 13 and the line sensor 14are disposed such that when the record medium 16 totally reflects thelaser light 17, an axis of the sensor 14A of the line sensor 14 in thelongitudinal direction is positioned on a plane to which light paths ofthe laser light 17 irradiated from the laser light source 13 and thereflected light 18 of the laser light 17 reflected by the record medium16 belong. Here, the axis of the sensor 14A in the longitudinaldirection is the center line of the light receiving surface of thesensor 14A in the longitudinal direction as designated by 14B in FIG. 3.

It is desirable that the plane to which the light paths belong issubstantially vertical to the conveyance direction of the record medium16 indicated by an arrow A.

Next, detection results of the reflected light 18 in the line sensor 14will be described. FIG. 5 is a view showing detection results of a casewhere the record medium 16 is a recycled paper. FIG. 5( b) is a graph inwhich the vertical axis indicates the intensity of the detectedreflected light 18, the horizontal axis indicates the received lightposition in the sensor 14A of the line sensor 14 having received thereflected light 18, and the detection results are plotted.

FIG. 5( a) is a view showing the detection results in which at eachreceived light position in the sensor 14A, a case of exceeding athreshold value is shown to be white (“1” when it is indicated by anumerical value), and a case of the threshold value or less is shown tobe black (“0” when it is indicated by a numerical value). Incidentally,performing binarization means making an expression with two values withreference to a threshold value.

Here, a distribution state means a state indicated by the detectedintensity of the reflected light 18 at each received light position inthe sensor 14A of the line sensor 14 having received the reflected light18.

In the case where the record medium 16 is such that the surface is notglossy and is rough like the recycled paper, the distribution state issuch that the intensity of the reflected light 18 is low in total, andthe reflected light 18 is detected in a wide range of the sensor 14A.

FIG. 6 is a view showing, similarly to FIG. 5, detection results of acase where the record medium 16 is a plain paper. In the case where therecord medium 16 is such that the surface is not glossy but is not veryrough, the distribution state is such that the intensity of thereflected light 18 is rather high in total, and the reflected light 18is concentrated on a portion of the sensor 14A and is detected.

FIG. 7 is a view showing, similarly to FIG. 5, detection results of acase where the record medium 16 is a glossy paper. In the case where therecord medium 16 is such that the surface is glossy and is not rough,the distribution state is such that the intensity of the reflected light18 is very high in total, and the reflected light 18 is concentrated onthe center portion of the sensor 14A and is widely detected.

As stated above, according to the embodiment, since the distributionstate varies according to the kind of the record medium 16, thedistribution state is compared with a previously determined distributionstate, and the kind of the record medium 16 is determined.

Next, a specific determination method will be described. Thedetermination method is not limited, and a well-known method or a newlycontrived method can be suitably selected. Hereinafter, a descriptionwill be given to a method (first application example) in which a Eucliddistance is compared, a method (second application example) in which adifference of detection values is compared, a method (third applicationexample) in which at the time of conveyance of the record medium 16, thelaser light 17 is irradiated for a definite time and a detected value isintegrated, and a method (fourth application example) in which thedetected value is averaged at each detection position and is compared.

FIRST APPLICATION EXAMPLE

The signal processing device 12 expresses detected values, that is, adistribution state by a vector. Each component may be a relative valueof the detected value or a binarized numerical value of 0 or 1. A columnrepresents a position on the sensor 14A.

In the case where there are eight detection positions and the binarizedvalues are used, an example of a vector X of detected values becomes

X1=(0, 1, 0, 0, 1, 1, 0, 0) X2=(0, 0, 1, 1, 1, 1, 1, 0).

Here, an example of a vector as reference, that is, a previouslydetermined distribution state is made

S1=(0, 1, 0, 0, 1, 0, 0, 0): recycled paperS2=(0, 1, 1, 1, 1, 1, 1, 0): glossy paper.The values are stored in a memory of the signal processing device 12 asa table or a part of a program.

Next, a Euclid distance D(a, b) between two points

a(a1, a2, . . . , an)b(b1, b2, . . . , bn)is defined as indicated below.

${D( {a,b} )} = \sqrt{\sum\limits_{i = 1}^{n}( {{ai} - {bi}} )^{2}}$

Next, the signal processing device 12 sequentially obtains the Eucliddistance D(a, b) between the vector of the detected values and thereference vector. The result is as follows:

D(X1, S1)=1 D(X1, S2)=3 D(X2, S1)=5 D(X2, S2)=1.

Further, the signal processing device 12 determines the relation betweenthe calculated Euclid distance D and a threshold value. When thethreshold value is made 2, it is determined that X1 is close to thedistribution of the state of S1 since the Euclid distance D with respectto S1 is the threshold or less and the Euclid distance D with respect toS2 is the threshold or more. In this way, the signal processing device12 determines that X1 is the recycled paper. Similarly, it is determinedthat X2 is close to the distribution of the state of S2, and the signalprocessing device 12 determines that X2 is the glossy paper.

According to the above example, the raw data of the detected values orthe relative values are used, and even if the number of columns isincreased, it is possible to determine the record medium 16.

SECOND APPLICATION EXAMPLE

The signal processing device 12 first expresses detected values, thatis, a distribution state by a vector. Each component may be a relativevalue of the detected value or a binarized numerical value of 0 or 1. Acolumn represents a position on the sensor 14A.

In the case where there are eight detection positions and the binarizedvalues are used, an example of a vector Xk of the detected valuesbecomes

X1 (0, 1, 0, 0, 1, 1, 0, 0) X2=(0, 0, 1, 1, 1, 1, 1, 0).

Here, a vector as reference, that is, an example of a previouslydetermined distribution state is made

S1=(0, 1, 0, 0, 1, 0, 0, 0): recycled paperS2=(0, 1, 1, 1, 1, 1, 1, 0): glossy paper.The values are stored in a memory of the signal processing device 12 asa table or a part of a program.

Next, a difference H(a, b) between two points

a(a1, a2, . . . , an)b(b1, b2 . . . , bn)is defined as indicated below.

${H( {a,b} )} = {\sum\limits_{i = 1}^{n}( {{ai} - {bi}} )}$

Next, the signal processing device 12 sequentially obtains thedifference H(a, b) between the vector of the detected values and thereference vector. The result is as follows:

H(X1, S1)=+1 H(X1, S2)=−2 H(X2, S1)=+3 H(X2, S2)=−1

Further, the signal processing device 12 determines the relation betweenthe calculated difference H and a threshold range. When the thresholdrange R is made −1≦R≦+1, the difference H between X1 and S1 is withinthe threshold range, and the difference H between X1 and S2 is outsidethe threshold range, and therefore, it is possible to determine that X1is close to the distribution of the state of S1. In this way, the signalprocessing device 12 determines that X1 is the recycled paper.Similarly, it is possible to determine that X2 is close to thedistribution of the state of S2, and the signal processing device 12determines that X2 is the glossy paper.

According to the above example, the raw data of the detected values orthe relative values are used, and even if the number of columns isincreased, it is possible to determine the record medium 16.

THIRD APPLICATION EXAMPLE

When the record medium 16 is being conveyed, the laser light source 13irradiates the laser light 17 to the record medium 16 for a definitetime. At this time, the line sensor 14 receives the reflected light 18of the laser light 17 from the record medium 16 for the definite time,and outputs an output signal converted into an electric signal to thesignal processing device 12.

The signal processing device 12 first expresses detected values, thatis, a distribution state by a vector. Each component may be a relativevalue of the detected value or a binarized numerical value of 0 or 1. Acolumn represents a position on the sensor 14A.

In the case where there are eight detection positions and the binarizedvalues are used, an example of a vector Xt of the detected valuesdetected at time t is

X1=(0, 1, 0, 1, 1, 1, 1, 0) X2=(0, 0, 1, 1, 1, 1, 1, 0) X3=(0, 1, 0, 1,1, 1, 1, 0).

Next, when detection is performed i times for the definite time, anintegrated value I of the detected values

a1(a11, a21, . . . , an1)a2(a12, a22, . . . , an2)ai(a1 i, a2 i, . . . , ani)is defined as indicated below. That is, the detected value is added ateach detection position, and a vector is calculated.

$I = ( {{\sum\limits_{k = 1}^{i}{a\; 1k}},{\sum\limits_{k = 1}^{i}{a\; 2k}},\ldots \mspace{11mu},{\sum\limits_{k = 1}^{i}{ank}}} )$

Next, the signal processing device 12 sequentially obtains theintegrated value I of the vector of the detected values. An example ofthe result is as follows:

I=(0, 2, 1, 3, 3, 3, 3, 0).

This integrated value I is compared with the reference vector inaccordance with the procedure described in the first application exampleor the second application example, and the kind of the record medium 16is determined.

According to the example, the raw data of the detected values or therelative values are used, and even if the number of columns isincreased, it is possible to determine the record medium 16.

FOURTH APPLICATION EXAMPLE

When the record medium 16 is being conveyed, the laser light source 13irradiates the laser light 17 to the record medium 16 for a definitetime. At this time, the line sensor 14 receives the reflected light 18of the laser light 17 from the record medium 16 for the definite time,and outputs an output signal converted into an electric signal to thesignal processing device 12.

The signal processing device 12 first expresses detected values, thatis, a distribution state by a vector. Each component may be a relativevalue of the detected value or a binarized numerical value of 0 or 1. Acolumn represents a position on the sensor 14A.

In the case where there are eight detection positions and the binarizedvalues are used, an example of a vector Xt of the detected valuesdetected at time t is

X1=(0, 1, 0, 1, 1, 1, 1, 0) X2=(0, 0, 1, 1, 1, 1, 1, 0) X3=(0, 1, 0, 1,1, 1, 1, 0).

Next, when detection is performed i times for the definite time, anaverage value B of the detected values

a1(a11, a21, . . . , an1)a2(a12, a22, . . . , an2)ai(a1 i, a2 i, . . . , ani)is defined as indicated below. That is, the detected value is added ateach detection position, and the result is divided by the number ofdetections to obtain an average value at each detection position, andthe vector is calculated.

$B = ( {{\frac{1}{i}{\sum\limits_{k = 1}^{i}{a\; 1k}}},{\frac{1}{i}{\sum\limits_{k = 1}^{i}{a\; 2k}}},\ldots \mspace{11mu},{\frac{1}{i}{\sum\limits_{k = 1}^{i}{ank}}}} )$

Next, the signal processing device 12 sequentially obtains the averagevalue B of the vector of the detected values. An example of the resultis as follows:

B=(0, 0.66, 0.33, 1, 1, 1, 1, 0).

When a value less than 1 is rounded to 0, this becomes as follows:

Br=(0, 0, 0, 1, 1, 1, 1, 0).

This average value Br is compared with the reference vector inaccordance with the procedure described in the first application exampleor the second application example, and the kind of the record medium 16is determined.

According to the example, the raw data of the detected values or therelative values are used, and even if the number of columns isincreased, it is possible to determine the record medium 16.

Next, a superior point obtained by using the line sensor 14 in thisembodiment will be described. FIG. 8 is a view showing comparison ofranges in which the reflected light 18 can be detected.

FIG. 8( c) is a view showing a state, seen from side, where the laserlight 17 is irradiated to the record medium 16 and the reflected light18 is generated. A dotted line 80 indicates the range of scatter of thereflected light 18 and the range where the reflected light 18 isdetected by a light detector such as the line sensor 14 or an areasensor.

FIG. 8( a) is a view showing a range 81 of the reflected light 18 whichcan be detected by the area sensor. Besides, FIG. 8( b) is a viewshowing a range 82 of the reflected light 18 which can be detected bythe sensor 14A of the line sensor 14. Reference character W denotes thelength of the sensor 14A of the line sensor 14 in the longitudinaldirection as shown in FIG. 3.

As a position approaches the periphery of the dotted line 80, theexistence of the reflected light 18 and its intensity reflect the stateof the surface of the record medium 16 sensitively. This is also shownin the drawings shown in FIGS. 5 to 7. Accordingly, in the device todetermine the kind of the record medium 16 by detecting the reflectedlight 18, it can be said that when the reflected light 18 is detected ina wider range, the determination accuracy becomes high.

Here, when FIG. 8( a) and FIG. 8( b) are compared with each other, it isunderstood that the range 82 in which the reflected light 18 can bedetected in the case where the line sensor 14 is used, that is, therange indicated by an alternate long and short dash line 84 is widerthan the range 81 where the reflected light 18 can be detected in thecase where the area sensor is used, that is, the range indicated by analternate long and short dash line 83, and the detection can be made tothe vicinity of the dotted line 80.

Accordingly, the detection accuracy of the record medium becomes higherwhen the line sensor is used than when the area sensor is used.

The record medium determining device 1 of the embodiment can beinstalled in the image forming apparatus. In the case where it isinstalled in the image forming apparatus, for example, the structure canbe made as follows. It is desirable that the record medium determiningdevice 1 is set at a position where the laser light 17 from the laserlight source 13 can be irradiated to the record medium 16, and a lightother than the light from the laser light source 13 is less incident onthe line sensor 14. The determination result of the record medium by therecord medium determining device 1 is outputted to a control unit of theimage forming apparatus, and the control unit of the image formingapparatus adjusts the printing method in accordance with thisdetermination result. Besides, the control unit of the image formingapparatus is constructed to control the operation of the record mediumdetermining device 1.

As described above, in this embodiment, the record medium determiningdevice 1 irradiates the laser light 17 to the surface of the recordmedium 16, the received light position and the received light intensityof the reflected light 18 are detected by the line sensor 14, and thekind of the record medium 16 is determined by comparing the distributionstate of the received light position and the received light intensitywith the previously determined distribution state. Thus, the range wherethe reflected light 18 can be detected is widened, and there is aneffect that more kinds of the record medium 16 can be determined withhigh accuracy.

<Image Forming Apparatus>

Next, the image forming apparatus will be described.

FIG. 9 is a view showing a structural example of the image formingapparatus. As shown in FIG. 9, a document stand 602 for mountingdocuments, which is formed of a transparent material such as a glassplate, is provided at an upper part of an apparatus main body 601. Acover 603 is openably and closably mounted on the apparatus main body601 so as to cover the document stand 602.

A scan unit (not shown) to optically read an image of an originaldocument mounted on the document stand 602 is provided at the lower sideof the document stand 602 in the inside of the apparatus main body 601.For example, the scan unit includes a carriage 604, reflecting mirrors606, 607 and 608 to reflect a light of an exposure lamp 605 reflected bythe original document, a scaling lens block 609 to scale the reflectedlight, and a CCD (Charge Coupled Device) 610. The carriage 604 isprovided with the exposure lamp 605 to irradiate the light to thedocument stand 602, and is constructed to be capable of reciprocatingalong the lower surface of the document stand 602.

The carriage 604 moves while the exposure lamp 605 is being turned on,so that the original document mounted on the document stand 602 isexposed. A reflected light image of the original document, which ismounted on the document stand 602, by the exposure is projected onto theCCD 610 through the reflecting mirrors 606, 607 and 608 and the scalinglens block 609. The CCD 610 outputs an image signal corresponding to theprojected reflected light image of the original document.

An image forming unit 220 is provided below the scan unit in the insideof the apparatus main body 601. The image forming unit 220 includes, forexample, a print engine (not shown) and a process unit (not shown).

The print engine includes an exposure unit 611. The process unitincludes photoconductive drums 621, 622, 623 and 624 arranged along theexposure unit 611, an endless transfer belt 625 arranged to be oppositeto the exposure unit 611 across the photoconductive drums 621, 622, 623and 624, a drive roller 626 to drive the transfer belt 625, primarytransfer rollers 641, 642, 643 and 644 arranged to be opposite to thephotoconductive drums 621, 622, 623 and 624 across the transfer belt625, and a transfer roller drive unit to drive the primary transferrollers 641, 642, 643 and 644.

The transfer belt 625 is stretched over a drive roller 626, guiderollers 627, 628 and 629 and a driven roller 630, receives power fromthe drive roller 626 and rotates and runs in the counterclockwisedirection. The guide roller 627 is provided to be freely moved up anddown, and receives the rotation of a cam 631 to be moved to the transferbelt 625 side. By this, the guide roller 627 displaces the transfer belt625 to the side of the photoconductive drums 621, 622, 623 and 624.

The image forming unit 220 executes an image formation process to forman image based on image data (image signal outputted from the CCD 610)and to print the image on the record medium being conveyed. That is,after the image signal outputted from the CCD 610 is suitably processed,it is supplied to the exposure unit 611. The exposure unit 611 emits alaser beam B1 corresponding to a yellow color image signal to thephotoconductive drum 621 for yellow, emits a laser beam B2 correspondingto a magenta color image signal to the photoconductive drum 622 formagenta, emits a laser beam B3 corresponding to a cyan color imagesignal to the photoconductive drum 623 for cyan, and emits a laser beamB4 corresponding to a black color image signal to the photoconductivedrum 624 for black.

The primary transfer rollers 641, 642, 643 and 644 are moved (lowered)to the transfer belt 625 side, so that the transfer belt 625 is broughtinto contact with the photoconductive drums 621, 622, 623 and 624, andvisible images on the photoconductive drums 621, 622, 623 and 624 aretransferred to the transfer belt 625.

A not-shown drum cleaner, a charge-removal lamp, a charging unit, and adeveloping unit are sequentially disposed around the photoconductivedrum 621. The drum cleaner includes a drum cleaning blade which comes incontact with the surface of the photoconductive drum 621, and scrapesaway a developer remaining on the surface of the photoconductive drum621 by the drum cleaning blade.

The charge-removal lamp removes a charge remaining on the surface of thephotoconductive drum 621. The charging unit applies a high voltage tothe photoconductive drum 621, so that the surface of the photoconductivedrum 621 is charged with an electrostatic charge. The laser beam B1emitted from the exposure unit 611 is irradiated to the surface of thecharged photoconductive drum 621. An electrostatic latent image isformed on the surface of the photoconductive drum 621 by thisirradiation. The developing unit supplies a yellow developer (toner) tothe surface of the photoconductive drum 621, so that the electrostaticlatent image on the surface of the photoconductive drum 621 is made avisible image.

Also in the other photoconductive drums 622, 623 and 624, similarly,developers of the corresponding colors are used and electrostatic latentimages on the surfaces of the respective photoconductive drums 622, 623and 624 are made visible images.

A cleaner 636 is provided at a position opposite to the drive roller 626of the image forming unit 220 across the transfer belt 625. This cleaner636 includes a cleaning blade 636 a which comes in contact with thetransfer belt 625, and scrapes away the developer remaining on thetransfer belt 625 by the cleaning blade 636 a.

The printing mode is changed as described below. Hooks 671, 672, 673 and674 are provided in the vicinities of the primary transfer rollers 641,642, 643 and 644. The hooks 671, 672, 673 and 674 are engaged withshafts of the primary transfer rollers 641, 642, 643 and 644 to raisethe shafts while rotating, and move the primary transfer rollers 641,642, 643 and 644 in the direction of separating from the photoconductivedrums 621, 622, 623 and 624. The printing mode, such as a full-colormode, all separation mode or a monochrome mode, is changed by not movingany of the primary transfer rollers 641, 642, 643 and 644 or by movingthem and changing the combination.

Next, a containing mechanism and a supply mechanism of record media willbe described. Plural record medium cassettes 650 to contain record mediaare provided below the exposure unit 611. In these record mediumcassettes 650, a number of record media P different from one another inrecord medium type are contained in a stacked state. A record mediumsupply mechanism 221 to supply the record medium in the record mediumcassette 650 one by one from above is provided at an exit portion (rightin the drawing) of each of the record medium cassettes 650. By thisrecord medium supply mechanism 221, the record medium P is taken out oneby one from any one of the record medium cassettes 650. The recordmedium supply mechanism 221 for taking out includes a pickup roller 651,a record medium supply roller 652 a, and a separating roller 652 b,separates the record medium P, which is taken out from the record mediumcassette 650, one by one, and supplies it to a record medium conveyancepath 653.

Next, the conveyance path of the record medium will be described. Therecord medium conveyance path 653 extends to an upper record mediumdischarge port 654 through the driven roller 630 of the image formingunit 220. The record medium discharge port 654 faces a record mediumdischarge unit 655 continuous with the outer peripheral surface of theapparatus main body 601. At the starting end side of the conveyance path653, a conveyance roller 656 is provided in the vicinity of each of therecord medium supply mechanisms 221. When the record medium is suppliedby one of the record medium supply mechanisms 221, the record mediumconveyance path 653 conveys the supplied record medium to the recordmedium discharge unit 655.

A secondary transfer roller 657 is provided at a halfway position of therecord medium conveyance path 653 where it is opposite to the drivenroller 630 across the transfer belt 625. A register roller 658 isprovided at an upstream position of the driven roller 630 and thesecondary transfer roller 657 in the conveyance direction.

At the timing in synchronization with the transfer operation as anoperation of transferring an image formed with a developer (toner) tothe record medium by the transfer belt 625 and the secondary transferroller 657, the register roller 658 sends the record medium P to betweenthe transfer belt 625 and the secondary transfer roller 657. Thesecondary transfer roller 657 holds the sheet record medium P sent fromthe register roller 658 between itself and the transfer belt 625 on thedriven roller 630, transfers the visible image formed with the developer(toner) and transferred on the transfer belt 625 to this record mediumP, and prints it. As stated above, the register roller 658 conveys therecord medium P to the image forming unit 220 including the transferbelt 625 and the secondary transfer roller 657 in synchronization withthe transfer operation of the image forming unit 220.

A heat roller 659 for heat fixation and a press roller 660 in contactwith the heat roller 659 are provided at a downstream position of therecord medium conveyance path 653 with respect to the secondary transferroller 657. The image transferred on the record medium P is fixed by theheat roller 659 and the press roller 660. Incidentally, a record mediumdischarge roller 661 is provided at the end of the record mediumconveyance path 653.

An auto duplex unit (hereinafter referred to as ADU) 222 may be providedin the apparatus main body 601. The ADU 222 is installed so as to couplea sub-conveyance path 662, which is a path for conveying the recordmedium P in the ADU 222, to the end of the record medium conveyance path653 and an inlet to the register roller 658. The sub-conveyance path 662branches away from the downstream side (end of the record mediumconveyance path 653) of the record medium conveyance path 653 withrespect to the image forming unit 220, and meets the upstream side(upstream side position of the register roller 658) of the record mediumconveyance path 653 with respect to the image forming unit 220.

The sub-conveyance path 662 reverses the obverse and reverse of therecord medium P for two-sided printing. The sub-conveyance path 662 isprovided with record medium supply rollers 663, 664 and 665, the ADU 222reversely sends the record medium P conveyed from the image forming unit220 to the record medium discharge unit 655, conveys it along thesub-conveyance path 662, and causes it to meet the record mediumconveyance path 653 at the upstream side of the image forming unit 220.When the conveyance is made in this way, the obverse and reverse of therecord medium P is reversed.

After the record medium P returned to the upstream side of the imageforming unit 220 by the sub-conveyance path 662 meets the record mediumconveyance path 653, the register roller 658 establishes synchronizationwith the transfer operation of the image forming unit 220, and therecord medium is sent to the transfer position where the transfer belt625 is in contact with the secondary transfer roller 657. As statedabove, the visible image on the transfer belt 625 is transferred also tothe reverse surface of the record medium P and is printed.

When the two-sided printing is specified by the operation panel 724provided on the apparatus main body 601 or the computer connected to theapparatus main body 601 through the network, the sub-conveyance path 662of the ADU 222 is brought into the state of performing the operation toreverse the obverse and reverse of the record medium P.

Next, an additionally provided device will be described. In the exampleof the apparatus main body 601 shown in FIG. 9, the two record mediumcassettes 650 are provided as the supply source of the record medium.Three or more record medium cassettes 650 may be provided in theapparatus main body 601. In addition, although not shown, a manual feedrecord medium supply mechanism such as a Stack Feed Bypass (hereinafterreferred to as SFB), or a large capacity record medium feeder(hereinafter referred to as LCF), which can contain several thousandrecord media in a stacked form, can also be provided. The SFB or the LCFis installed in the apparatus main body 601 so that the path to supplythe record medium meets the record medium conveyance path 653.

Next, the installation position of the record medium determining device1 of the embodiment will be described. FIG. 10 is a view showing thevicinity of the record medium conveyance path 653 in detail.Hereinafter, a combination of the heat roller 659 and the press roller660 is called a fixing unit 721. In this fixing unit 721, the heatroller 659 heats the record medium P on which the developer (toner) istransferred, and the press roller 660 conveys it while applyingpressure, so that the developer is fixed to the record medium P.

The apparatus main body 601 is provided with a not-shown control unit.This control unit can be constructed of, for example, a CPU, a memorysuch as a ROM or a RAM, an LSI and the like. The control unit controlsthe temperature of the heat roller 659. For example, in the case wherethere is no signal from the control unit, the heat roller 659 keeps apreviously determined temperature according to the kind of the recordmedium P and is on standby, and in the case where a signal of fixationstart is received, the temperature is changed in accordance with theinstruction.

Since the apparatus main body 601 has the structure as stated above andfixes the developer, the record medium determining device 1 is disposedon the upstream side of the record medium conveyance path 653 withrespect to the fixing unit 721.

In the case where only one record medium determining device 1 is used,it is installed at a first installation position 223 shown in FIG. 9.The first installation position 223 is the upstream side of the recordmedium conveyance path 653 with respect to the image forming unit 220,and is the upstream side position of the register roller 658. In thecase where the SFB 712 or the LCF 705 is installed, the firstinstallation position 223 is the downstream side position of the meetingpoint between the record medium supply path from the SFB 712 and the LCF705 and the record medium conveyance path 653. The record mediumdetermining device 1 is installed to face the surface of the recordmedium to be conveyed.

The record medium determining device 1 is arranged at the firstinstallation position 223, so that the one record medium determiningdevice 1 can detect the kinds of the record media P conveyed on therecord medium conveyance path 653 from all record medium supply sources.

According to the model of the image forming apparatus, there is a casewhere the installation can not be performed at the first installationposition 223 according to the relation of the arrangement of variousparts in the inside of the apparatus main body 601. Besides, there isalso a model in which the SFB 712 is attached as an option. In thesecases, the record medium determining device 1 can also be disposed atthe following two places.

A description will be made by use of FIG. 10. A second installationposition 715 is a position in the record medium conveyance path 653, onthe upstream side of the record medium conveyance path 653 with respectto the image forming unit 220 and on the upstream side of the registerroller 658 and is a position on the downstream side with respect to therecord medium supply roller 652 a and the separating roller 652 b of theuppermost stage cassette device 650, and on the downstream side of themeeting position between the record medium supply path from the LCF 705and the record medium conveyance path 653. The record medium determiningdevice 1 is disposed to face the surface of the record medium to beconveyed. The record medium determining device 1 may be installed in thevicinity of the conveyance roller 656 at the second installationposition 715.

A third installation position 718 is a position on the upstream side ofthe meeting position between the record medium supply path from the SFB712 and the record medium conveyance path 653. The record mediumdetermining device 1 is installed to face the surface of the recordmedium to be conveyed. The record medium determining device 1 may beinstalled in the vicinity of a conveyance roller 717 at the thirdinstallation position 718.

When the record medium determining device 1 is disposed at the secondinstallation position 715 and the third installation position 718, inthe model in which the SFB 712 is attached as an option, there is aneffect that the record medium determining device 1 can be installed atthe installation position 718 as the need arises.

Next, a description will be given to an application example relating tothe processing of a signal of determination result outputted from therecord medium determining device 1. An operation panel 724 which selectsthe kind of the record medium P and is also used for display ofinformation and for input at the time of data setting is attached to theupper surface of the apparatus main body 601. The operation panel 724 isconnected to the control unit. The control unit controls the speed of amotor to rotate and drive each roller for conveying the record medium,and performs also the stop and restart of conveyance of the recordmedium.

First, the control unit stores the default kind of the record medium orthe kind of the record medium inputted by the operation panel 724 intothe memory as the set record medium, and sets the standby temperature ofthe heat roller 659 according to the set record medium.

Next, the record medium P is conveyed, and when the record mediumdetermining device 1 determines the kind of the record medium P, therecord medium determining device 1 outputs a signal of determinationresult to the control unit. In accordance with the determination result,the control unit sets, for example, the conveyance speed of the recordmedium, the rotation speed of the fixing unit 721, and the temperatureof the heat roller 659 at the time of fixing, and transmits instructionsto these devices.

As stated above, the image forming apparatus of this application examplefirst sets the set record medium, and next, further sets the conditions,such as the speed at the time of fixing and the temperature, inaccordance with the kind of the record medium determined by the recordmedium determining device 1. Thus, there is an effect that the finercondition setting at the time of fixing according to the kind of therecord medium and the execution of the fixing can be quickly performed.

Although exemplary embodiments of the present invention have been shownand described, it will be apparent to those having ordinary skill in theart that a number of changes, modifications, or alterations to theinvention as described herein may be made, none of which depart from thespirit of the present invention. All such changes, modifications, andalterations should therefore be seen as within the scope of the presentinvention.

1. A record medium determining device comprising: a laser light sourceto irradiate a laser light to a surface of a record medium; a linesensor to receive a reflected light of the laser light from the recordmedium and to output an output signal converted into an electric signal,wherein the line sensor detects a received light position in the linesensor having received the reflected light and a received lightintensity of the received reflected light from the output signal; and asignal processing device to determine a kind of the record medium bycomparing a distribution state of the received light position and thereceived light intensity with a previously determined distributionstate.
 2. The record medium determining device according to claim 1,wherein when the record medium totally reflects the laser light, theline sensor is arranged so that an axis of a sensor of the line sensorin a longitudinal direction is positioned on a plane to which a lightpath of the laser light irradiated from the laser light source andreflected by the record medium belongs.
 3. The record medium determiningdevice according to claim 1, wherein when the record medium is beingconveyed, the laser light source irradiates the laser light to therecord medium for a definite time, the line sensor receives thereflected light of the laser light from the record medium for thedefinite time and outputs the output signal converted into the electricsignal, and the signal processing device compares a distribution stateof an average of the received light intensity for the definite time atthe received light position with a previously determined distributionstate, and determines the kind of the record medium.
 4. The recordmedium determining device according to claim 1, wherein when the recordmedium is being conveyed, the laser light source irradiates the laserlight to the record medium for a definite time, the line sensor receivesthe reflected light of the laser light from the record medium for thedefinite time and outputs the output signal converted into the electricsignal, and the signal processing device compares a distribution stateof an integrated value of the received light intensity for the definitetime at the received light position with a previously determineddistribution state, and determines the kind of the record medium.
 5. Therecord medium determining device according to claim 1, wherein a lengthof a sensor of the line sensor in a longitudinal direction is not lessthan 5 mm and is not larger than a length of a maximum record medium tobe determined in the longitudinal direction.
 6. An image formingapparatus for forming an image on a record medium, comprising: a recordmedium supply mechanism to supply a record medium one by one; a recordmedium conveyance path for conveying the record medium supplied from therecord medium supply mechanism to a record medium discharge unit; animage forming unit that is arranged on an upstream side of the recordmedium conveyance path with respect to the record medium discharge unitand executes an image forming process to print an image based on imagedata to the record medium conveyed through the record medium conveyancepath; a fixing unit to fix a developer to the record medium at aspecified temperature; a record medium determining device that isdisposed on an upstream side of the record medium conveyance path withrespect to the fixing unit and detects a kind of the record medium; anda control unit to change a condition at a time when the image formingprocess is executed according to the kind of the record mediumdetermined by the record medium determining device, wherein the recordmedium determining device comprises: a laser light source to irradiate alaser light to a surface of the record medium; a line sensor to receivea reflected light of the laser light from the record medium and tooutput an output signal converted into an electric signal, wherein theline sensor detects a received light position in the line sensor havingreceived the reflected light and a received light intensity of thereceived reflected light from the output signal; and a signal processingdevice to determine the kind of the record medium by comparing adistribution state of the received light position and the received lightintensity with a previously determined distribution state.